Cellular Phone Application Specific RAM

Transcription

1 Cellular Phone Application Specific RAM Mobile FCRAM TM with High-Speed Page Mode A further enhanced Mobile FCRAM featuring a high-speed page mode, a 1.8V power supply operation. Introduction Besides the simple function of voice calling, cellular phones in recent years are coming out with sophisticated capabilities such as , Internet connection, and music distribution. To keep up with this trend, the memory modules built into cellular phones have to offer higher throughput and larger storage densities. Two years ago, FUJITSU commenced mass-production and shipment of MB82D01160 and MB82D01161, a pair of 16M-bit Mobile FCRAM devices configured with a highspeed, power-saving memory FCRAM specially designed by FUJITSU as a alternative to Low Power SRAMs used in conventional cellular phones. At the time, these devices were endowed with the world s largest RAM density for cellular phones. In the year after their release they were adopted in many second-generation and 2.5-generation cellular phones. The Mobile FCRAM supports an asynchronous SRAM type interface, one of the standard memory interfaces for cellular phones. This encourages system designers to install the FCRAM without changing any existing system configurations. Once the Mobile FCRAM was introduced into market, FUJITSU s Mobile FCRAM and other large-density psuedo- SRAM devices became another standard option for installation in the cellular phones used widely in Japan (in addition to the two conventionally available options, NOR-type flash memory and Low Power SRAM). This trend of adopting the Mobile Photo 1 External View Photo 2 Chip 48 FIND Vol.20 No

2 FCRAM as a alternative to SRAMs is taking root in overseas cellular phone markets, where full-scale introduction and emerging demand are expected in the future. Demand for Mobile FCRAM is expected to increase dramatically in the third-generation cellular communication standards. Japan has stepped ahead of Europe in offering preliminary WCDMA services, and the requirements for high-performance, largedensity RAM are pressing. The newly developed device, 32M-bit Mobile FCRAM () is the first of the Mobile FCRAM to support a high-speed page mode function that dramatically improves performance when consecutive address access occurs within the same page. In addition to page mode, the device integrates additional new feature suited for the target market. is the world first FCRAM to operate with 1.8V power supply in-line with the market trend of today s GSM and GPRS, European mobile communication standards, where migration from 3V to 1.8V of the power supply is ahead of the other cellular phone standards including PDC and cdma in Japan. Features Asynchronous SRAM interface 2M-word 16-bit configuration Supply voltage: 1.65V to 1.95V Operating temperature range: 30 to 85 8-word high-speed page mode Power-down function 48-pin FBGA package Available in a form of chip or wafer Stacked MCP with Flash Memory (Part # is different) Table 1 Main Characteristics Table 2 Function Truth Table 2002 No.4 FIND Vol.20 49

3 Figure 1 CE1 Access Time vs. Supply Voltage Characteristics Figure 2 Page Address Access Time vs. Supply Voltage Characteristics Figure 3 High-Speed Page Mode Timing 50 FIND Vol.20 No

4 Characteristics Table 1 lists the principal characteristics and Table 2 lists the functions incorporated. Fig. 1 shows the CE1 access time vs. supply voltage characteristics and Fig. 2 shows the page address access time vs. supply voltage characteristics. Functions High-speed page mode This product is the first Mobile FCRAM to support the high-speed page mode, which is a high-speed access feature to the same page accelerates data-intensive read operations that are continuously repeated. This product supports an 8- word page size. Fig. 3 shows the operation timing in the high-speed page mode. Power-down mode This product features an enhanced power-down function Table 3 Power-down Function FUJITSU offers. The power down is a function specialized to Work Memory applications. There is the case that the data stored in Work Memory are not necessary to be retained once CPU goes into standby state. Upon this usage, the device put in power down mode substantially reduces its power supply current (power down current IDDP 10 A) by stopping to maintain data for the selected part of memory array, thereby extending the battery life (a key factor for cellular phones). Table 3 lists the selection of power-down modes which are user programable featurs. (See the data sheet for details.) Entry to and exit from the power-down mode are controlled by the CE2 input signal. Fig. 4 shows the detailed timing for the power-down mode entry and exit. Future Development Fig. 5 traces the development trend for Mobile FCRAM. FUJITSU s Mobile FCRAMs have been evolving. The density has increased (16M-bit 32M-bit 64M-bit 128M-bit), the access time has steadily evolved (90ns to 80ns 70ns to 60ns page mode advanced features), and the supply voltage has improved from 3V to 1.8V. FUJITSU puts the emphasis on three key factors as it work on to provide the right solutions for customer needs: larger density, higher speed, and more energy saving. Figure 4 Power-down Mode Timings 2002 No.4 FIND Vol.20 51

5 NOTES * FCRAM ( Fast Cycle RAM) is a trademark of FUJITSU LIMITED. ** Mobile FCRAM is a pseudo-sram product consists of the FCRAM core and asynchoronous SRAM interface. Figure 5 Mobile FCRAM Roadmap 52 FIND Vol.20 No